Catheters are elongate hollow tubes that are used to transmit fluids into or out of the body of a patient. Conventions followed for the devices described in this disclosure are that the term "proximal" is the direction away from the patient and toward the practitioner and the term "distal" refers to the direction toward the patient and away from the practitioner. There are many types of catheters currently used in medical practice. Some catheters are sufficiently strong and rigid to be introduced by themselves, urinary catheters are examples of this type of catheter. Another catheter type is positioned on the outside of a sharp introducer needle and slid down over the needle into the patient's body using the needle to make the penetration and provide a guide to placement of the catheter, many intravenous catheters are of this type. This disclosure is related to yet another type, a catheter that is introduced into the patient through the bore of a sharp introducer needle. Through-the-needle catheters are further separated into two types by the introducer needle. When a through-the-needle catheter has a fixed hub for attachment of a fluid handling device, the introducer needle cannot be slid off the proximal end of the catheter. Catheters with fixed hubs either are used with a splittable introducer needle or the needle must be left on the catheter. One important application of catheters in medical practice is the use of long flexible catheters to introduce medicaments, often anesthetic or analgesic formulations, into the spine of a patient. In this application, the long (50-75 cm) flexible catheter tubing (generally 19-21 gauge) is introduced into the patient's epidural space through the bore of an introducer needle.
These spinal anesthesia procedures are widely used in hospital practice, with the generic name of "an epidural." As an example, the use of an epidural anesthetic is described in obstetric practice. The epidural anesthetic procedure is useful in many other type of procedures. In a typical obstetric procedure, the epidural catheter is often placed early in the patient's labor with the patient lying on her side, then the patient is placed on her back with the knees elevated for the rest of the delivery. Since the patient is on her back, the introducer needle generally must be removed. Most epidural catheters do not have fixed hubs thus allowing the introducer needle to be slid proximally off of the catheter and removed. Once the needle is removed, it is necessary to mount an adapter onto the catheter so that a fluid handling device such as a syringe may be attached to the catheter. The adapter is then often secured with tape onto the patient's body. The Tuohy-Borst adapter was developed for this application. The Tuohy-Borst adapter allows a fluid handling device with a male luer fitting to be mounted onto a small diameter (generally 19-21 gauge: Nominal Outside Diameters for these 19 to 21 gauges are between about 1.10 mm [19 gauge] to about 0.8 mm [21 gauge]) flexible catheter tube. The original Tuohy-Borst adapter is formed from metal and is considered reusable. Other variants of the original Tuohy-Borst are now available formed from thermoplastics. The thermoplastic adapters are generally supplied sterile and are considered single-use and disposable. The Tuohy-Borst type adapters all depend in some degree on a threaded collar being screwed down around the catheter to compress a resilient plug contained in a body portion. The seal around the catheter is formed by compressing the tip of the resilient plug into a cavity around the catheter tube by screwing the collar down onto the plug. In most of these adapters, it is easy for a practitioner to inadvertently over-tighten the threaded collar and occlude the catheter lumen. Alternatively, if the collar is not tightened down sufficiently, the adapter may leak or may even come off of the catheter tube. Most of the available adapters are generally cylindrical, may include a releasable latch mechanism and require at least about one-half rotation of the collar portion with respect to the body portion to secure the adapter onto the catheter.
A widely used adapter, available from B. Braun, Bethlehem, Pa., has a collar and a body portion. The Braun adapter is capable of almost four complete rotations of the collar with respect to the body portion from the initial engagement of the threads. Additionally, if this collar of the B. Braun adapter is fully unthreaded from the body portion, it may detach and allow disassembly of the adapter. Another widely used adapter is the disposable successor to the reusable Tuohy-Borst available from Becton Dickinson and Company, Franklin Lakes, N.J. The collar of this successor adapter is fully seated on the body after only about two and one half rotations of the collar with respect to the body. Additionally, unlike the B. Braun adapter, the collar is retained on the body when completely unthreaded so that it cannot easily fall off Another available adapter, as disclosed in U.S. Pat. Nos. 5,053,015 and 5,226,898, has an external ratchet and includes small wings on both the body and the collar to facilitate the practitioners handling and, when the wings are aligned, provides some indication that the adapter is secured onto the tubing. When the adapter disclosed in the referenced patents is secured to the patient's body, the small wings may cause discomfort to the patient, and additionally, the adapter may sometimes be difficult for a gloved practitioner to handle.
Other than the catheter adapters disclosed in U.S. Pat. Nos. 5,053,015 and 5,226,898, substantially all of the available adapters do not provide the practitioner with much indication of the sufficiency of the degree of tightness of the collar with respect to the body, and it is not easily visually apparent if the collars are loosened so that the catheter tubing may be inserted into the adapter or if the collar is partially screwed down on the body, making it difficult to insert the catheter tube into the adapter body. Operating room time is expensive, and additionally, many procedures are conducted under time constraints that potentially have impact on the patient's well being. As a result, practitioners and their support staff make every effort to set up repeatable procedures with standardized placements of equipment to facilitate rapid implementation of procedures. If a practitioner attempts to put an adapter onto a catheter tube and has difficulty because the adapter is partially threaded, additional time is required. If a practitioner inadvertently over-tightens a collar of an adapter occluding the lumen, he may believe the catheter is clogged or kinked, remove it and have to repeat the placement. The repeat procedure not only subjects the patient to additional risk, but also significantly increases the time required. If an adapter is not sufficiently tightened, it may fall off or leak during an extended procedure, thereby resulting in improper patient medication. If a gloved practitioner has difficulty handling an adapter and drops it, there may be a time delay while another adapter is procured, and, in the case where the adapter is part of a procedure kit, another whole kit, with a significant cost increment, may need to be opened just to obtain another adapter.
If a catheter adapter that was easily handled by a gloved practitioner was available that provided the practitioner with a positive indication of its status, i.e., ready-to-receive a catheter tube or fully tightened; that could not be over-tightened; and required only about one quarter turn of the collar with respect to the body to be fully tightened, the art of catheter adapters would be advanced. Such a catheter adapter is disclosed below.